1. Field of the Invention
The present invention relates to an image recording apparatus in which at least one of a positive photosensitive material of which density becomes low (white) during development processing with an increase in exposure amount and a negative photosensitive material of which density becomes high (black) during development processing with an increase in exposure amount can be loaded as kinds of photosensitive materials and is conveyed onto an exposure stage, and an image is recorded on the conveyed photosensitive material in such a manner that amounts of light of three colors emitted from a light source are controlled based on image data of an original.
2. Description of the Related Art
A number of image recording apparatuses each having a digital exposure system mounted thereon has been nowadays developed. Generally, in the digital exposure system, an image is recorded on a recording medium in such a manner that a light beam outputted from a semiconductor laser is modulated with image data and the light beam is deflected by high-speed rotation of a polygon mirror (main scanning), and further the light beam reflected by the polygon mirror is subjected to sub-scanning with a galvano mirror or the like, or the above main scanning is effected repeatedly while moving the recording medium (or moving the recording medium stepwise). Here, as the recording medium, a photosensitive drum electrified by corona discharge, a plane photosensitive material, or the like may be used. Further, in place of the semiconductor laser, other light emitter such as an LED may be used as a light source.
On the other hand, the recording mediums (photosensitive materials) used by the image recording apparatus as described above can be classified into a photosensitive material having a positive characteristic and a photosensitive material having a negative characteristic.
It is generally known that the photosensitive material having a positive characteristic (hereinafter referred to as a positive photosensitive material) becomes white by exposure-development processing to facilitate reproduction of black. Further, it is generally known that the photosensitive material having a negative characteristic (hereinafter referred to as a negative photosensitive material) becomes black by exposure-development processing to facilitate reproduction of white.
In the case of the positive photosensitive material, the degree at which it becomes white is made higher with an increase of exposure amount. In the case of the negative photosensitive material, the degree at which it becomes black is made higher with an increase of exposure amount. For this reason, when white is reproduced on the positive photosensitive material and when black is reproduced on the negative photosensitive material, it is necessary to increase an amount of light emitted from a light source to the maximum level, and therefore, a problem occurs in the aspect of heat generated from the light source and durability.
In other words, these photosensitive materials have both merits and demerits. However, presently, any one of the positive and negative photosensitive materials is used (the negative photosensitive material is used more frequently than the other).